208 – Diffraction of Light

Diffraction at the single slit 

 

Introduction to:  

  • Diffraction  
  • Monochromatic light  

Material:

  • Laser pointer   
  • Laser safety goggles  
  • Sharp Knife  
  • Fastening material (clothespins / paper clips / adhesive tape)  
  • Strong paper (e.g. construction paper, approx. 7 cm x 20 cm, approx. 130-200 g/m²)  
  • Ruler   
  • Support for laser (possibly height-adjustable)  
  • Cutting surface (hard, stable)  
  • Sheet of white paper  

Instructions:   

  • Cut a straight slit in the construction paper with the help of the knife and ruler.   
  • The width of the gap should be about 0.1 mm.  
  • Attach the paper to the ruler with the fastening material and place it at a distance of about 2 m from a wall.  
  • Set up the laser in such a way that the laser beam hits the gap in the construction paper straight at a distance of about 15 cm.  
  • Always use the safety goggles.  
  • Attach the sheet of paper as a screen to the point where the light beam hits the wall.  
  • Darken the room.

Observation:  

  • The light spot on the screen is not point-shaped, but elongated in the direction perpendicular to the slit.  

Explication: 

  • The light is diffracted at the edges of the gap.  

Tips: 

  • Move the laser beam back and forth slightly with the contact surface to set an optimal result.